Additives for low-sulfur mineral oil distillates, comprising aromatics which bear a hydroxyl group, a methoxy group and an acid function

ABSTRACT

The invention provides an additive for fuel oils, comprising at least one copolymer of ethylene and an unsaturated ester, at least one oil-soluble polar nitrogen compound which is a reaction product of amines of the formula NR 6 R 7 R 8  in which R 6 , R 7  and R 8  may be the same or different, and at least one of these groups is C 8 -C 36 -alkyl, C 6 -C 36 -cycloalkyl, C 8 -C 36 -alkenyl, especially C 12 -C 24 -alkyl, C 12 -C 24 -alkenyl or cyclohexyl, and the remaining groups are hydrogen, C 1 -C 36 -alkyl, C 2 -C 36 -alkenyl, cyclohexyl or a group of the formulae -(A-O) x -E or —(CH 2 ) n —NYZ in which A is an ethyl or propyl group, x is from 1 to 50, E=H, C 1 -C 30 -alkyl, C 5 -C 12 -cycloalkyl or C 6 -C 30 -aryl, and n=2, 3 or 4, and Y and Z are each independently H, C 1 -C 30 -alkyl or -(A-O) x  with compounds which contain at least one acyl group, and at least one aromatic compound of the formula 1,  
                 
 
in which R is H or C 1 - to C 4 -alkyl.

The invention relates to additives for low-sulfur mineral oil distillates with improved cold flowability and paraffin dispersancy, comprising an additive based on hydroxyl-methoxyphenylcarboxylic acid, to fuel oils additized therewith and to the use of the additive.

In view of the decreasing mineral oil reserves coupled with steadily rising energy demand, ever more problematic crude oils are being extracted and processed. In addition, the demands on the fuel oils produced therefrom, such as diesel and heating oil, are becoming ever more stringent, not least as a result of legislative requirements. Examples thereof are the reduction in the sulfur content and the limitation of the final boiling point and also of the aromatics content of middle distillates, which force the refineries into constant adaptation of the processing technology. In middle distillates, this leads in many cases to an increased proportion of paraffins, especially in the chain length range of from C₁₈ to C₂₄, which in turn has a negative influence on the cold flow properties of these fuel oils.

Crude oils and middle distillates, such as gas oil, diesel oil or heating oil, obtained by distillation of crude oils contain, depending on the origin of the crude oils, different amounts of n-paraffins which crystallize out as platelet-shaped crystals when the temperature is reduced and sometimes agglomerate with the inclusion of oil. This crystallization and agglomeration causes a deterioration in the flow properties of these oils or distillates, which may result in disruption in the course of extraction, transport, storage and/or use of the mineral oils and mineral oil distillates. When mineral oils are transported through pipelines, the crystallization phenomenon can, especially in winter, lead to deposits on the pipe walls, and in individual cases, for example in the event of stoppage of a pipeline, even to its complete blockage. When the mineral oils are stored and processed further, it may also be necessary in winter to store the mineral oils in heated tanks. In the case of mineral oil distillates, the consequence of crystallization may be blockages of the filters in diesel engines and boilers, which prevents reliable metering of the fuels and under some circumstances results in complete interruption of the fuel or heating medium feed.

In addition to the classical methods of eliminating the crystallized paraffins (thermally, mechanically or using solvents), which merely involve the removal of the precipitates which have already formed, chemical additives (known as flow improvers) have been developed in recent years. By interacting physically with the precipitating paraffin crystals, they bring about modification of their shape, size and adhesion properties. The additives function as additional crystal seeds and some of them crystallize out with the paraffins, resulting in a larger number of smaller paraffin crystals having altered crystal shape. The modified paraffin crystals have a lower tendency to agglomerate, so that the oils admixed with these additives can still be pumped and processed at temperatures which are often more than 20° C. lower than in the case of nonadditized oils.

Typical flow improvers for crude oils and middle distillates are co- and terpolymers of ethylene with carboxylic esters of vinyl alcohol.

A further task of flow improvers is the dispersion of the paraffin crystals, i.e. the retardation or prevention of the sedimentation of the paraffin crystals and therefore the formation of a paraffin-rich layer at the bottom of storage vessels.

EP-A-0 061 895 discloses cold flow improvers for mineral oil distillates, which comprise esters, ethers or mixtures thereof. The esters/ethers contain two linear saturated C₁₀- to C₃₀-alkyl groups and a polyoxyalkylene group with from 200 to 5000 g/mol.

EP-0 973 848 and EP-0 973 850 disclose mixtures of esters alkoxylated alcohols with more than 10 carbon atoms and fatty acids with 10-40 carbon atoms in combination with ethylene copolymers as flow improvers.

EP-A-0 935 645 discloses alkylphenol-aldehyde resins as a lubricity-improving additive in low-sulfur middle distillates.

EP-A-0 857 776 and EP-A-1 088 045 disclose processes for improving the flowability of paraffin-containing mineral oils and mineral oil distillates by addition of ethylene copolymers and alkylphenol-aldehyde resins, and also optionally further nitrogen-containing paraffin dispersants.

WO-99/62973 discloses the use of copolymers of dialkylphenyl fumarate and a comonomer selected from vinyl acetate, styrene, C₃- to C₃₀-α-olefins, ethylene and carbon monoxide as a cold additive for oils.

It is therefore an object of the invention to improve the flowability and especially the paraffin dispersancy under cold conditions in mineral oils or mineral oil distillates by the addition of suitable cold additives.

It has now been found that, surprisingly, aromatic compounds which contain hydroxyl, methoxy and carboxyl groups are highly suitable for paraffin dispersancy in mineral oils and mineral oil distillates.

The invention thus provides an additive for fuel oils, comprising at least one copolymer of ethylene and an unsaturated ester, at least one oil-soluble polar nitrogen compound which is a reaction product of amines of the formula NR⁶R⁷R⁸ in which R⁶, R⁷ and R⁸ may be the same or different, and at least one of these groups is C₈-C₃₆-alkyl, C₆-C₃₆-cycloalkyl, C₈-C₃₆-alkenyl, especially C₁₂-C₂₄-alkyl, C₁₂-C₂₄-alkenyl or cyclohexyl, and the remaining groups are hydrogen, C₁-C₃₆-alkyl, C₂-C₃₆-alkenyl, cyclohexyl or a group of the formulae -(A-O)_(x)-E or —(CH₂)_(n)—NYZ in which A is an ethyl or propyl group, x is from 1 to 50, E=H, C₁-C₃₀-alkyl, C₅-C₁₂-cycloalkyl or C₆-C₃₀-aryl, and n=2, 3 or 4, and Y and Z are each independently H, C₁-C₃₀-alkyl or -(A-O)_(x) with compounds which contain at least one acyl group, and at least one aromatic compound of the formula 1,

in which R is H or C₁- to C₄-alkyl.

The invention further provides fuel oils comprising at least one copolymer of ethylene and an unsaturated ester, at least one oil-soluble polar nitrogen compound which is a reaction product of amines of the formula NR⁶R⁷R⁸ in which R⁶, R⁷ and R⁸ may be the same or different, and at least one of these groups is C₈-C₃₆-alkyl, C₆-C₃₆-cycloalkyl, C₈-C₃₆-alkenyl, especially C₁₂-C₂₄-alkyl, C₁₂-C₂₄-alkenyl or cyclohexyl, and the remaining groups are hydrogen, C₁-C₃₆-alkyl, C₂-C₃₆-alkenyl, cyclohexyl or a group of the formulae -(A-O)_(x)-E or —(CH₂)_(n)—NYZ in which A is an ethyl or propyl group, x is from 1 to 50, E=H, C₁-C₃₀-alkyl, C₅-C₁₂-cycloalkyl or C₆-C₃₀-aryl, and n=2, 3 or 4, and Y and Z are each independently H, C₁-C₃₀-alkyl or -(A-O)_(x) with compounds which contain at least one acyl group, and at least one aromatic compound of the formula 1,

in which R is H or C₁- to C₄-alkyl.

The invention further provides for the use of the inventive additives in amounts of from 5 to 10 000 ppm as a paraffin dispersent in fuel oils, preferably in middle distillates.

The invention further provides a process for improving the cold flow properties of fuel oils, comprising the addition of from 5 to 10 000 ppm of the inventive additives to the fuel oil.

The above-specified aromatic compounds of the formula 1 are referred to hereinbelow as aromatic additives. Particular preference is given to 4-hydroxy-3-methoxyphenylpropionic acid or 4-hydroxy-3-methoxycinnamic acid.

The aromatic additives are added to middle distillates, irrespective of their content of copolymers of ethylene and an unsaturated ester, preferably in amounts of from 10 to 1000 ppm, in particular from 20 to 500 ppm.

The additive for fuel oils is referred to hereinbelow as inventive additive.

In addition to the aromatic additive, the inventive additives also comprise one or more copolymers of ethylene and unsaturated esters and optionally further olefinically unsaturated compounds. Suitable ethylene copolymers are in particular those which, in addition to ethylene, contain from 6 to 21 mol %, in particular from 10 to 18 mol % of unsaturated esters. These copolymers preferably have melt viscosities at 140° C. of from 20 to 10 000 mPas, in particular from 30 to 5000 mPas, especially from 50 to 2000 mPas.

The unsaturated esters are preferably vinyl esters, acrylic esters and/or methacrylic esters.

The further olefinically unsaturated compounds are preferably alkyl vinyl ethers and/or alkenes, which may be substituted by hydroxyl groups.

In addition to ethylene, one or more comonomers may be present in the copolymer.

The vinyl esters are preferably those of the formula 2 CH₂═CH—OCOR¹  (2) where R¹ is C₁- to C₃₀-alkyl, preferably C₄- to C₁₆-alkyl, especially C₆- to C₁₂-alkyl. In a further embodiment, the alkyl groups mentioned may be substituted by one or more hydroxyl groups.

In a further preferred embodiment, R¹ is a branched alkyl radical or a neoalkyl radical having from 7 to 11 carbon atoms, in particular having 8, 9 or 10 carbon atoms. Particularly preferred vinyl esters derive from secondary and especially tertiary carboxylic acids whose branch is in the alpha-position to the carbonyl group. Suitable vinyl esters include vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl hexanoate, vinyl heptanoate, vinyl octanoate, vinyl pivalate, vinyl 2-ethylhexanoate, vinyl laurate, vinyl stearate and Versatic esters such as vinyl neononanoate, vinyl neodecanoate, vinyl neoundecanoate.

In a further preferred embodiment, these ethylene copolymers contain vinyl acetate and at least one further vinyl ester of the formula 4 where R¹ is C₄- to C₃₀-alkyl, preferably C₄- to C₁₆-alkyl, especially C₆- to C₁₂-alkyl.

The (meth)acrylic esters are preferably those of the formula 3 CH₂═CR²—COOR³  (3) where R² is hydrogen or methyl and R³ is C₁- to C₃₀-alkyl, preferably C₄- to C₁₆-alkyl, especially C₆- to C₁₂-alkyl. Suitable acrylic esters include, for example, methyl(meth)acrylate, ethyl(meth)acrylate, propyl(meth)acrylate, n- and isobutyl(meth)acrylate, hexyl, octyl, 2-ethylhexyl, decyl, dodecyl, tetradecyl, hexadecyl, octadecyl(meth)acrylate and mixtures of these comonomers. In a further embodiment, the alkyl groups mentioned may be substituted by one or more hydroxyl groups. An example of such an acrylic ester is hydroxyethyl methacrylate.

The alkyl vinyl ethers are preferably compounds of the formula 4 CH₂═CH—OR⁴  (4) where R⁴ is C₁- to C₃₀-alkyl, preferably C₄- to C₁₆-alkyl, especially C₆- to C₁₂-alkyl. Examples include methyl vinyl ether, ethyl vinyl ether, isobutyl vinyl ether. In a further embodiment, the alkyl groups mentioned may be substituted by one or more hydroxyl groups.

The alkenes are preferably monounsaturated hydrocarbons having from 3 to 30 carbon atoms, in particular from 4 to 16 carbon atoms and especially from 5 to 12 carbon atoms. Suitable alkenes include propene, butene, isobutylene, pentene, hexene, 4-methylpentene, octene, diisobutylene and norbornene and derivatives thereof such as methylnorbornene and vinylnorbornene. In a further embodiment, the alkyl groups mentioned may be substituted by one or more hydroxyl groups.

Apart from ethylene, particularly preferred terpolymers contain from 0.1 to 12 mol %, in particular from 0.2 to 5 mol %, of vinyl neononanoate or of vinyl neodecanoate, and from 3.5 to 20 mol %, in particular from 8 to 15 mol %, of vinyl acetate, the total comonomer content being between 6 and 21 mol %, preferably between 12 and 18 mol %.

Further particularly preferred copolymers contain, in addition to ethylene and from 8 to 18 mol % of vinyl esters, also from 0.5 to 15 mol % of alkenes as described above.

Preference is given to using mixtures of two or more of the abovementioned ethylene copolymers. The polymers on which the mixtures are based more preferably differ in at least one feature.

For example, they may contain different comonomers, or different comonomer contents, molecular weights and/or degrees of branching.

The mixing ratio between the aromatic additives, the ethylene copolymers and the oil-soluble polar nitrogen compounds may, depending on the application, vary within wide limits, the ethylene copolymers and the oil-soluble polar nitrogen compounds often constituting the major proportion. The inventive additives preferably contain from 2 to 70% by weight, preferably from 5 to 50% by weight of the aromatic additive, and also from 30 to 98% by weight, preferably from 50 to 95% by weight of ethylene copolymers, and also the oil-soluble polar nitrogen compounds. Examples of concentrations are from 0.1 to 100 ppm, preferably from 1 to 50 ppm, in particular from 5 to 50 ppm of aromatic additive, from 20 to 500 ppm, preferably from 50 to 400 ppm, in particular from 75 to 350 ppm of ethylene copolymer and from 20 to 500 ppm, preferably from 50 to 400 ppm, in particular from 75 to 350 ppm of oil-soluble polar nitrogen compounds.

The suitable oil-soluble polar nitrogen compounds (constituent II) are reaction products of fatty amines with compounds which contain an acyl group. The preferred amines are compounds of the formula NR⁶R⁷R⁸ where R⁶, R⁷ and R⁸ may be the same or different, and at least one of these groups is C₈-C₃₆-alkyl, C₆-C₃₆-cycloalkyl or C₈-C₃₆-alkenyl, in particular C₁₂-C₂₄-alkyl, C₁₂-C₂₄-alkenyl or cyclohexyl, and the remaining groups are either hydrogen, C₁-C₃₆-alkyl, C₂-C₃₆-alkenyl, cyclohexyl, or a group of the formulae -(A-O)_(x)-E or —(CH₂)_(n)—NYZ, where A is an ethyl or propyl group, x is from 1 to 50, E=H, C₁-C₃₀-alkyl, C₅-C₁₂-cycloalkyl or C₆-C₃₀-aryl, and n=2, 3 or 4, and Y and Z are each independently H, C₁-C₃₀-alkyl or -(A-O)_(x). The alkyl and alkenyl radicals may each be linear or branched and contain up to two double bonds. They are preferably linear and substantially saturated, i.e. they have iodine numbers of less than 75 g of I₂/g, preferably less than 60 g of I₂/g and in particular between 1 and 10 g of I₂/g. Particular preference is given to secondary fatty amines in which two of the R⁶, R⁷ and R⁸ groups are each C₈-C₃₆-alkyl, C₆-C₃₆-cycloalkyl, C₈-C₃₆-alkenyl, in particular C₁₂-C₂₄-alkyl, C₁₂-C₂₄-alkenyl or cyclohexyl. Suitable fatty amines are, for example, octylamine, decylamine, dodecylamine, tetradecylamine, hexadecylamine, octadecylamine, eicosylamine, behenylamine, didecylamine, didodecylamine, ditetradecylamine, dihexadecylamine, dioctadecylamine, dieicosylamine, dibehenylamine and mixtures thereof. The amines especially contain chain cuts based on natural raw materials, for example coconut fatty amine, tallow fatty amine, hydrogenated tallow fatty amine, dicoconut fatty amine, ditallow fatty amine and di(hydrogenated tallow fatty amine). Particularly preferred amine derivatives are amine salts, imides and/or amides, for example amide-ammonium salts of secondary fatty amines, in particular of dicoconut fatty amine, ditallow fatty amine and distearylamine.

Acyl group refers here to a functional group of the following formula: >C═O

Carbonyl compounds suitable for the reaction with amines are either low molecular weight or polymeric compounds having one or more carboxyl groups. Preference is given to those low molecular weight carbonyl compounds having 2, 3 or 4 carbonyl groups. They may also contain heteroatoms such as oxygen, sulfur and nitrogen. Suitable carboxylic acids are, for example, maleic acid, fumaric acid, crotonic acid, itaconic acid, succinic acid, C₁-C₄₀-alkenylsuccinic acid, adipic acid, glutaric acid, sebacic acid and malonic acid, and also benzoic acid, phthalic acid, trimellitic acid and pyromellitic acid, nitrilotriacetic acid, ethylenediaminetetraacetic acid and their reactive derivatives, for example esters, anhydrides and acid halides. Useful polymeric carbonyl compounds have been found to be in particular copolymers of ethylenically unsaturated acids, for example acrylic acid, methacrylic acid, maleic acid, fumaric acid and itaconic acid; particular preference is given to copolymers of maleic anhydride. Suitable comonomers are those which confer oil solubility on the copolymer. Oil-soluble means here that the copolymer, after reaction with the fatty amine, dissolves without residue in the middle distillate to be additized in practically relevant dosages. Suitable comonomers are, for example, olefins, alkyl esters of acrylic acid and methacrylic acid, alkyl vinyl esters, alkyl vinyl ethers having from 2 to 75, preferably from 4 to 40 and in particular from 8 to 20, carbon atoms in the alkyl radical. In the case of olefins, the alkyl radical attached to the double bond is equivalent here. The molecular weights of the polymeric carbonyl compounds are preferably between 400 and 20 000, more preferably between 500 and 10 000, for example between 1000 and 5000.

It has been found that oil-soluble polar nitrogen compounds which are obtained by reaction of aliphatic or aromatic amines, preferably long-chain aliphatic amines, with aliphatic or aromatic mono-, di-, tri- or tetracarboxylic acids or their anhydrides are particularly useful (cf. U.S. Pat. No. 4,211,534). Equally suitable as oil-soluble polar nitrogen compounds are amides and ammonium salts of aminoalkylenepolycarboxylic acids such as nitrilotriacetic acid or ethylenediaminetetraacetic acid with secondary amines (cf. EP 0 398 101). Other oil-soluble polar nitrogen compounds are copolymers of maleic anhydride and α,β-unsaturated compounds which may optionally be reacted with primary monoalkylamines and/or aliphatic alcohols (cf. EP-A-0 154 177, EP 0 777 712), the reaction products of alkenyl-spiro-bislactones with amines (cf. EP-A-0 413 279 B1) and, according to EP-A-0 606 055 A2, reaction products of terpolymers based on α,β-unsaturated dicarboxylic anhydrides, α,β-unsaturated compounds and polyoxyalkylene ethers of lower unsaturated alcohols.

The mixing ratio between the inventive additives and oil-soluble polar nitrogen compounds as constituent II may vary depending upon the application. Such additive mixtures preferably contain from 5 to 95% by weight, preferably from 10 to 90% by weight of the inventive additive, and also from 5 to 95% by weight, preferably from 10 to 90% by weight of oil-soluble polar nitrogen compounds.

In addition to the aromatic additives, the ethylene copolymers and the oil-soluble polar nitrogen compounds, further constituents may be present as coadditives in the fuel oils or in the inventive additive. For instance, olefin copolymers may be used as a coadditive in the inventive additives.

Suitable olefin copolymers as a coadditive for the inventive additive (constituent III) may derive directly from monoethylenically unsaturated monomers, or may be prepared indirectly by hydrogenation of polymers which derive from polyunsaturated monomers such as isoprene or butadiene. Preferred copolymers contain, in addition to ethylene, structural units which derive from α-olefins having from 3 to 24 carbon atoms and have molecular weights of up to 120 000 g/mol. Preferred α-olefins are propylene, butene, isobutene, n-hexene, isohexene, n-octene, isooctene, n-decene, isodecene. The comonomer content of olefins is preferably between 15 and 50 mol %, more preferably between 20 and 35 mol % and especially between 30 and 45 mol %. These copolymers may also contain small amounts, for example up to 10 mol %, of further comonomers, for example nonterminal olefins or nonconjugated olefins. Preference is given to ethylene-propylene copolymers. The olefin copolymers may be prepared by known methods, for example by means of Ziegler or metallocene catalysts.

Further suitable olefin copolymers are block copolymers which contain blocks composed of olefinically unsaturated aromatic monomers A and blocks composed of hydrogenated polyolefins B. Particularly suitable block copolymers have the structure (AB)_(n)A and (AB)_(m), where n is from 1 to 10 and m is from 2 to 10.

The mixing ratio between the inventive additive and constituent III is generally in each case between 1:20 and 20:1, preferably in each case between 1:10 and 10:1 by weight.

In the inventive additive, comb polymers may also be used as a coadditive.

Suitable comb polymers as a coadditive for the inventive additive (constituent IV) may be described, for example, by the formula 5

In this formula

A is R′, COOR′, OCOR′, R″—COOR′, OR′;

D is H, CH₃, A or R″;

E is H, A;

G is H, R″, R″—COOR′, an aryl radical or a heterocyclic radical;

M is H, COOR″, OCOR″, OR″, COOH;

N is H, R″, COOR″, OCOR″, an aryl radical;

R′ is a hydrocarbon chain having from 8 to 50 carbon atoms;

R″ is a hydrocarbon chain having from 1 to 10 carbon atoms;

In a preferred embodiment, alkylphenol-aldehyde resins are used as further constituents in the inventive additives (constituent V). Alkylphenol-aldehyde resins are known in principle and are described, for example, in Römpp Chemie Lexikon, 9th edition, Thieme Verlag 1988-92, volume 4, p. 3351 ff. Suitable in accordance with the invention are in particular those alkylphenol-aldehyde resins which derive from alkylphenols having one or two alkyl radicals in the ortho- and/or para-position to the OH group. Particularly preferred starting materials are alkylphenols which bear, on the aromatic ring, at least two hydrogen atoms capable of condensation with aldehydes, and especially monoalkylated phenols whose alkyl radical is in the para-position. The alkyl radicals (for constituent V, this refers generally to hydrocarbon radicals as defined below) may be the same or different in the alkylphenol-aldehyde resins usable in the process according to the invention, they may be saturated or unsaturated and have 1-200, preferably 1-20, in particular 4-12 carbon atoms; they are preferably n-, iso- and tert-butyl, n- and isopentyl, n- and isohexyl, n- and isooctyl, n- and isononyl, n- and isodecyl, n- and isododecyl, tetradecyl, hexadecyl, octadecyl, tripropenyl, tetrapropenyl, poly(propenyl) and poly(isobutenyl) radicals.

Suitable aldehydes for the alkylphenol-aldehyde resins are those having from 1 to 12 carbon atoms and preferably those having from 1 to 4 carbon atoms, for example formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, 2-ethylhexanal, benzaldehyde, glyoxalic acid and reactive equivalents thereof, such as paraformaldehyde and trioxane. Particular preference is given to formaldehyde in the form of paraformaldehyde and especially formalin.

In the context of the present patent application, molecular weights are always measured by means of gel permeation chromatography (GPC) against polystyrene standards in THF.

The molecular weight of the alkylphenol-aldehyde resins is preferably 400-20 000 g/mol, especially 400-5000 g/mol. A prerequisite in this context is that the alkylphenol-aldehyde resins are oil-soluble at least in concentrations relevant to the application of from 0.001 to 1% by weight.

In a preferred embodiment of the invention, the alkylphenol-formaldehyde resins contain oligo- or polymers having a repeat structural unit of the formula 3

where R⁵ is C₁-C₂₀₀-alkyl or -alkenyl and n is from 2 to 100. R⁵ is preferably C₄-C₂₀-alkyl or -alkenyl and especially C₆-C₁₆-alkyl or -alkenyl. n is preferably from 2 to 50 and especially from 3 to 25, for example from 5 to 15.

For use in middle distillates such as diesel and heating oil, particular preference is given to alkylphenol-aldehyde resins having C₂-C₄₀-alkyl radicals of the alkylphenol, preferably having C₄-C₂₀-alkyl radicals, for example C₆-C₁₂-alkyl radicals. The alkyl radicals may be linear or branched; they are preferably linear. Particularly suitable alkylphenol-aldehyde resins derive from linear alkyl radicals having 8 and 9 carbon atoms. The average molecular weight, determined by means of GPC, is preferably between 700 and 20 000 g/mol, in particular between 800 and 10 000 g/mol, for example between 1000 and 2500 g/mol.

These alkylphenol-aldehyde resins are obtainable by known processes, for example by condensation of the appropriate alkylphenols with formaldehyde, i.e. with from 0.5 to 1.5 mol, preferably from 0.8 to 1.2 mol of formaldehyde per mole of alkylphenol. The condensation may be effected without solvent, but is preferably effected in the presence of a water-immiscible or only partly water-miscible inert organic solvent such as mineral oils, alcohols, ethers and the like. Particular preference is given to solvents which can form azeotropes with water. Useful such solvents are in particular aromatics such as toluene, xylene, diethylbenzene and relatively high-boiling commercial solvent mixtures such as ®Shellsol AB and Solvent Naphtha. The condensation is effected preferably between 70 and 200° C., for example between 90 and 160° C. It is catalyzed typically by from 0.05 to 5% by weight of bases or acids. For example, the condensation catalyzed by amines, preferably tertiary amines, for example triethylamine, with subsequent neutralization by means of organic sulfonic acid leads to the suitable products. Preference is given in accordance with the invention to catalysis by organic sulfonic acids which, on completion of the condensation with amines, are converted to the oil-soluble ammonium sulfonates.

The mixing ratio of the alkylphenol-aldehyde resins as a coadditive to the inventive additive is generally between 20:1 and 1:20, preferably between 1:10 and 10:1.

In the inventive additive, polyoxyalkylene compounds may also be used as coadditives.

Suitable polyoxyalkylene compounds as a coadditive for the inventive additive (constituent VI) are, for example, esters, ethers and ether/esters which bear at least one alkyl radical having from 12 to 30 carbon atoms. When the alkyl groups stem from an acid, the remainder stems from a polyhydric alcohol; when the alkyl radicals come from a fatty alcohol, the remainder of the compound stems from a polyacid.

Suitable polyols are polyethylene glycols, polypropylene glycols, polybutylene glycols and copolymers thereof having a molecular weight of from approx. 100 to approx. 5000 g/mol, preferably from 200 to 2000 g/mol. Also suitable are alkoxylates of polyols, for example of glycerol, trimethylolpropane, pentaerythritol, neopentyl glycol, and the oligomers which are obtainable therefrom by condensation and have from 2 to 10 monomer units, for example polyglycerol. Preferred alkoxylates are those having from 1 to 100 mol, in particular from 5 to 50 mol, of ethylene oxide, propylene oxide and/or butylene oxide per mole of polyol. Esters are particularly preferred.

Fatty acids having from 12 to 26 carbon atoms are preferred for the reaction with the polyols to form the ester additives, and particular preference is given to using C₁₈- to C₂₄-fatty acids, especially stearic and behenic acid. The esters may also be prepared by esterifying polyoxyalkylated alcohols. Preference is given to fully esterified polyoxyalkylated polyols having molecular weights of from 150 to 2000, preferably from 200 to 600. Particularly suitable are PEG-600 dibehenate and glycerol ethylene glycol tribehenate.

The mixing ratio between the inventive additive and the further constituent VI is generally between 1:10 and 10:1, preferably in each case between 1:5 and 5:1.

The inventive additive may be used alone or in a mixture with one or more of constituent(s) II, III, IV, V or VI.

The inventive additives may be used alone or else together with other additives, for example with other pour point depressants or dewaxing assistants, with antioxidants, flow improvers, cetane number improvers, dehazers, demulsifiers, detergents, lubricity additives, dispersants, antifoams, dyes, corrosion inhibitors, sludge inhibitors, odorants and/or additives for lowering the cloud point. The other additives may be added directly to the fuel oil mixture or be introduced into the mixture by mixing different fuel oil components which have already been additized individually with one or more of the additives mentioned.

The inventive additives are suitable for improving the cold flow properties of fuel oils of animal, vegetable or mineral origin. In addition, they disperse the paraffins which precipitate out below the cloud point in middle distillates. In particular, they are superior to the prior art additives in problematic oils having a low aromatics content of less than 25% by weight, in particular less than 22% by weight, for example less than 20% by weight, of aromatics, and thus lower solubility for n-paraffins. Middle distillates refer in particular to those mineral oils which are obtained by distillation of crude oil and boil in the range from 120 to 450° C., for example kerosene, jet fuel, diesel and heating oil. Aromatic compounds refer to the totality of mono-, di- and polycyclic aromatic compounds, as can be determined by means of HPLC to DIN EN 12916 (2001 edition). The inventive additives are particularly advantageous in those middle distillates which contain less than 350 ppm of sulfur, more preferably less than 100 ppm of sulfur, in particular less than 50 ppm of sulfur and in special cases less than 10 ppm of sulfur. They are generally those middle distillates which have been subjected to refining under hydrogenating conditions and therefore contain only small fractions of polyaromatic and polar compounds. They are preferably those middle distillates which have 90% distillation points below 360° C., in particular 350° C. and in special cases below 340° C.

In view of decreasing world mineral oil reserves and the discussion about the environmentally damaging consequences of the use of fossil and mineral fuels, there is increasing interest in alternative energy sources based on renewable raw materials. These include in particular native oils and fats of vegetable or animal origin. These are generally triglycerides of fatty acids having from 10 to 24 carbon atoms and a calorific value comparable to conventional fuels, but are at the same time classified as biodegradable and environmentally compatible.

Oils obtained from animal or vegetable material are mainly metabolism products which include triglycerides of monocarboxylic acids, for example acids having from 10 to 25 carbon atoms, and corresponding to the formula

where R is an aliphatic radical which has from 10 to 25 carbon atoms and may be saturated or unsaturated.

In general, such oils contain glycerides from a series of acids whose number and type vary with the source of the oil, and they may additionally contain phosphoglycerides. Such oils can be obtained by processes known from the prior art.

As a consequence of the sometimes unsatisfactory physical properties of the triglycerides, the industry has applied itself to converting the naturally occurring triglycerides to fatty acid esters of lower alcohols such as methanol or ethanol. The prior art also includes mixtures of middle distillates with oils of vegetable or animal origin (also referred to hereinbelow as “biofuel oils”).

In a preferred embodiment, the biofuel oil, which is frequently also referred to as biodiesel or biofuel, comprises fatty acid alkyl esters composed of fatty acids having from 12 to 24 carbon atoms and alcohols having from 1 to 4 carbon atoms. Typically, a relatively large portion of the fatty acids contains one, two or three double bonds. The biofuel is more preferably, for example, rapeseed oil methyl ester and especially mixtures which comprise rapeseed oil fatty acid methyl ester, sunflower oil fatty acid methyl ester, palm oil fatty acid methyl ester, used oil fatty acid methyl ester and/or soya oil fatty acid methyl ester.

Examples of oils which are derived from animal or vegetable material and which can be used in the inventive fuel oils are rapeseed oil, coriander oil, soya oil, cottonseed oil, sunflower oil, castor oil, olive oil, peanut oil, maize oil, almond oil, palm kernel oil, coconut oil, mustardseed oil, bovine tallow, bone oil and fish oils. Further examples include oils which are derived from wheat, jute, sesame, shea tree nut, arachis oil and linseed oil, and can be derived therefrom by processes known from the prior art. It is also possible to use oils which have been obtained from used oils such as deep fat fryer oil. Preference is given to rapeseed oil, which is a mixture of fatty acids partially esterified with glycerol, since it is obtainable in large amounts and is obtainable in a simple manner by extractive pressing of rapeseeds. In addition, preference is given to the likewise widely available oils of sunflowers and soya, and also to their mixtures with rapeseed oil.

Useful lower alkyl esters of fatty acids are the following, for example as commercial mixtures: the ethyl, propyl, butyl and in particular methyl esters of fatty acids having from 12 to 22 carbon atoms, for example of lauric acid, myristic acid, palmitic acid, palmitolic acid, stearic acid, oleic acid, elaidic acid, petroselic acid, ricinolic acid, elaeostearic acid, linoleic acid, linolenic acid, eicosanoic acid, gadoleic acid, docosanoic acid or erucic acid, each of which preferably has an iodine number of from 50 to 150, in particular from 90 to 125. Mixtures having particularly advantageous properties are those which comprise mainly, i.e. comprise at least 50% by weight of, methyl esters of fatty acids having from 16 to 22 carbon atoms, and 1, 2 or 3 double bonds. The preferred lower alkyl esters of fatty acids are the methyl esters of oleic acid, linoleic acid, linolenic acid and erucic acid.

Commercial mixtures of the type mentioned are obtained, for example, by hydrolyzing and esterifying animal and vegetable fats and oils, by transesterifying them with lower aliphatic alcohols. To prepare lower alkyl esters of fatty acids, it is advantageous to start from fats and oils having a high iodine number, for example sunflower oil, rapeseed oil, coriander oil, castor oil, soya oil, cottonseed oil, peanut oil or bovine tallow. Preference is given to lower alkyl esters of fatty acids based on a novel type of rapeseed oil, whose fatty acid component is derived to an extent of more than 80% by weight from unsaturated fatty acids having 18 carbon atoms.

When mixtures of middle distillate of mineral origin (A) and biofuels (B) are used, the A:B mixing ratio of the constituents may vary as desired. It is preferably between A:B=99.9:0.1 and 0.1:99.9, in particular from 99:1 to 1:99, especially from 95:5 to 5:95, for example from 85:15 to 15:85 or from 80:20 to 20:80.

It is also possible to use mixtures of synthetic fuels, as are obtainable, for example, from the Fischer-Tropsch process, and a middle distillate of mineral origin A and/or a biofuel B as the fuel oil composition.

EXAMPLES

TABLE 1 Characterization of the test oils: The test oils employed were current oils from European refineries. The CFPP value was determined to EN 116 and the cloud point to ISO 3015. The aromatic hydrocarbon groups were determined to DIN EN 12916 (November 2001 edition) Test oil 1 Test oil 2 Test oil 3 Test oil 4 Test oil 5 Distillation IBP [° C.] 166.3° C. 173.8° C. 240.7 173.8 166.6 90%-20% cut [° C.]   147° C.   117° C. 64.4 116.6 102.5 FBP [° C.] 377.9° C. 345.7° C. 345.7 352.6 359.4 Cloud Point [° C.] −8.0 −6.7 −8.2 −6.9 −3.9 CFPP [° C.] −11.0 −8.0 −11 −9 −7 Sulfur [ppm] 308 210 1450 320 2.7 Density @15° C. [g/cm³] 0.826 0.831 0.841 0.827 0.845 Aromatics content [% by wt.] 18.73 27.50 24.16 27.96 26.63 of which mono [% by wt.] 14.31 22.22 15.76 22.58 23.89 di [% by wt.] 3.93 4.83 7.93 4.91 2.54 poly [% by wt.] 0.49 0.46 0.47 0.48 0.19

The following additives were used:

Characterization of the Ethylene Copolymers Used as Flow Improvers

The ethylene copolymers used were commercial products having the properties reported in Table 2. The products were used in the form of 65% and 50% dilutions in kerosene.

The viscosity was determined to ISO 3219/B with a rotational viscometer (Haake RV20) with plate-cone measuring system at 140° C. TABLE 2 Characterization of the ethylene copolymers used Example Comonomer(s) V₁₄₀ A1 13.6 mol % of vinyl acetate 130 mPas A2 12.5 mol % of vinyl acetate and 1.2 mol % of 150 mPas vinyl neodecanoate A3  9.8 mol % of vinyl acetate and 0.6 mol % of 170 mPas vinyl neodecanoate Characterization of the Further Additives Used (Constituent II):

B1) Polar polymeric nitrogen compound consisting of a comb polymer prepared from 1.3 mol % of 1-tetradecene, 1.3 mol % of hexadecene, 2.6 mol % of maleic anhydride and 0.2 mol % of allyl methyl polyglycol ether. The resulting polymer has a K value of 15 and is reacted with 2.6 mol % each of distearylamine and dicoconut fatty amine to give the amide ammonium salt. The titratable base nitrogen content of the 50% polymer solution is 0.69%.

Characterization of the Aromatic Additives

-   1) 4-Hydroxy-3-methoxyphenylpropionic acid -   2) 4-Hydroxy-3-methoxycinnamic acid -   3) 3-Hydroxy-4-methoxybenzaldehyde (comparison)     Effectiveness of the Additives as Cold Flow Improvers

To assess the effect of the inventive additives on the cold flow properties of middle distillates, the inventive additives were tested in middle distillates as follows in the short sediment test:

150 ml of the middle distillates admixed with the additive components specified in the table were cooled in 200 ml measuring cylinders in a cold cabinet at −2° C./hour to −13° C. and stored at this temperature for 16 hours. Subsequently, volume and appearance, both of the sedimented paraffin phase and of the oil phase above it, were determined and assessed visually. A small amount of sediment and an opaque oil phase show good paraffin dispersancy.

In addition, the lower 20% by volume is isolated and the cloud point is determined to ISO 3015. Only a slight deviation of the cloud point of the lower phase (CP_(cc)) from the blank value of the oil shows good paraffin dispersancy.

The aromatic additives reported are used in an amount of 50-150 ppm. A dispersant is used generally in the presence of a cold flow improver. In addition to the inventive additives, appropriate cold flow improvers were therefore used.

Results in Test Oil 1

The CFPP effectiveness and dispersing action of the inventive additives (constituent I) were determined in a composition of (by parts by weight) 50 ppm of the aromatic additive with 100 ppm of B1 and 400 ppm of A2. Aromatic CFPP CP_(cc) Example additive [° C.] [° C.] Visual assessment 1 1 −26 −7.6 Homogeneously opaque, no sediment 2 2 −27 −7.9 Homogeneously opaque, no sediment 3 (C) 3 (C) −22 −5.2 5 ml of sediment, homogeneously opaque Results in Test Oil 2

The CFPP effectiveness and dispersing action of the inventive additives (constituent I) were determined in a composition of (by parts by weight) 100 ppm of the aromatic additive with 150 ppm of B1 and 300 ppm of A2. CFPP CP_(cc) Example Aromatic additive [° C.] [° C.] Visual assessment 4 1 −27 −6.1 Homogeneously opaque, no sediment 5 2 −28 −6.5 Homogeneously opaque, no sediment 6 (C) 3 (C) −21 −4.7 8 ml of sediment Results in Test Oil 3

The CFPP effectiveness and dispersing action of the inventive additives (constituent I) were determined in a composition of (by parts by weight) 50 ppm of the aromatic additive with 100 ppm of B1 and 200 ppm of A3. CFPP CP_(cc) Example Aromatic additive [° C.] [° C.] Visual assessment 7 1 −23 −7.9  1 ml of sediment, homogeneously opaque 8 2 −24 −8.1 Homogeneously opaque, no sediment 9 (C) 3 (C) −19 −6.8 12 ml of sediment, homogeneously opaque Results in Test Oil 4

The CFPP effectiveness and dispersing action of the inventive additives (constituent I) were determined in a composition of (by parts by weight) 50 ppm of the aromatic additive with 200 ppm of B1 and 300 ppm of A3. Aromatic CFPP CP_(cc) Example additive [° C.] [° C.] Visual assessment 10 1 −29 −3.2 Homogeneously opaque, no sediment 11 2 −28 −3.5 Homogeneously opaque, no sediment 12 (C) 3 (C) −23 −1.2 11 ml of sediment, homogeneously opaque Results in Test Oil 5

The CFPP effectiveness and dispersing action of the inventive additives (constituent I) were determined in a composition of (by parts by weight) 100 ppm of the aromatic additive with 200 ppm of B1 and 300 ppm of A1. Aromatic CFPP Example additive [° C.] CP_(cc) [° C.] Visual assessment 13 1 −25 −7.5 Homogeneously opaque, no sediment 14 2 −27 −7.1 Homogeneously opaque, no sediment 15 (C) 3 (C) −22 −4.9 15 ml of sediment, homogeneously opaque 

1. An additive for fuel oils, comprising at least one copolymer of ethylene and an unsaturated ester, at least one oil-soluble polar nitrogen compound which is a reaction product of amines of the formula NR⁶R⁷R⁸ in which R⁶, R⁷ and R⁸ may be the same or different, and at least one of R⁶, R⁷ and R⁸ is C₈-C₃₆-alkyl, C₆-C₃₆-cycloalkyl, C₈-C₃₆-alkenyl, and the remaining groups are hydrogen, C₁-C₃₆-alkyl, C₂-C₃₆-alkenyl, cyclohexyl or a group of the formulae -(A-O)_(x)-E or —(CH₂)_(n)—NYZ in which A is an ethyl or propyl group, x is from 1 to 50, E=H, C₁-C₃₀-alkyl, C₅-C₁₂-cycloalkyl or C₆-C₃₀-aryl, and n=2, 3 or 4, and Y and Z are each independently H, C₁-C₃₀-alkyl or -(A-O)_(x) with compounds which contain at least one acyl group, and at least one aromatic compound of the formula 1,

in which R is H or C₁- to C₄-alkyl.
 2. The additive as claimed in claim 1, in which the aromatic compound of the formula 1 is 4-hydroxy-3-methoxyphenylpropionic acid or 4-hydroxy-3-methoxycinnamic acid, or a mixture thereof.
 3. The additive as claimed in claim 1, in which the ethylene copolymer, in addition to ethylene, comprises from 6 to 21 mol % of unsaturated esters.
 4. The additive of claim 1, in which the unsaturated ester is selected from the group consisting of vinyl ester, acrylic ester, methacrylic ester and mixtures there of.
 5. The additive of claim 1, in which, in addition to ethylene, two or more comonomers are present in the at least one copolymer.
 6. The additive of claim 1, in which the copolymer of ethylene comprises an aklene having from 3 to 30 carbon atoms as a comonomer.
 7. The additive of claim 1, further comprising an alkylphenol-aldehyde resin which is derived from an alkylphenol having one or two alkyl radicals having 1-200 carbon atoms in the ortho- or para-position or in the ortho- and the para-positions to the OH group and aldehydes having from 1 to 12 carbon atoms.
 8. The additive as claimed in claim 7, wherein the alkylphenol-formaldehyde resin has a repeat unit of the formula 3

in which R⁵ is C₁-C₂₀₀-alkyl or -alkenyl and n is from 2 to 100 in a weight ratio of from 1:20 to 20:1 based on the weight of the additive comprising the copolymer of ethylene and an unsaturated ester and the aromatic compound of the formula 1

in which R is H or C₁- to C₄-alkyl.
 9. The additive of claim 1, further comprising comb polymers of the formula 5

in which A is R′, COOR′, OCOR′, R″-COOR′, OR′; D is H, CH₃, A or R″; E is H, A; G is H, R″, R″—COOR′, an aryl radical or a heterocyclic radical; M is H, COOR″, OCOR″, OR″, COOH; N is H, R″, COOR″, OCOR″, an aryl radical; R′ is a hydrocarbon chain having from 8 to 50 carbon atoms; R″ is a hydrocarbon chain having from 1 to 10 carbon atoms; m is from 0.4 to 1.0; and n is from 0 to 0.6.
 10. The additive of claim 1, further comprising a polyoxyalkylene compound selected from the group consisting of esters, ethers and ether/esters having at least one alkyl radical having from 12 to 30 carbon atoms.
 11. A fuel oil comprising an oil selected from the group consisting of animal, vegetable, mineral origin, and mixtures thereof, at least one copolymer of ethylene and an unsaturated ester, at least one oil-soluble polar nitrogen compound which is a reaction product of amines of the formula NR⁶R⁷R⁸ in which R⁶, R⁷ and R⁸ may be the same or different, and at least one of R⁶, R⁷ and R⁸ is C₈-C₃₆-alkyl, C₆-C₃₆-cycloalkyl, C₈-C₃₆-alkenyl, and the remaining R⁶, R⁷ and R⁸ are hydrogen, C₁-C₃₆-alkyl, C₂-C₃₆-alkenyl, cyclohexyl or a group of the formulae -(A-O)_(x)-E or —(CH₂)_(n)—NYZ in which A is an ethyl or propyl group, x is from 1 to 50, E=H, C₁-C₃₀-alkyl, C₅-C₁₂-cycloalkyl or C₆-C₃₀-aryl, and n=2, 3 or 4, and Y and Z are each independently H, C₁-C₃₀-alkyl or -(A-O)_(x) with compounds which contain at least one acyl group, and at least one aromatic compound of the formula 1,

in which R is H or C₁- to C₄-alkyl.
 12. The fuel oil as claimed in claim 11, wherein the oil is a mixture selected from the group consisting of synthetic fuel, a middle distillate of mineral origin, a biofuel oil, and mixtures thereof.
 13. The fuel oil as claimed in claim 12, wherein the oil is a mixture of a middle distillate of mineral origin and a biofuel oil, and a mixing ratio of the middle distillate to the biofuel oil is from 99:1 to 1:99.
 14. A method for dispersing paraffins in a fuel oil, said method comprising adding from 5 to 10 000 ppm of the additive of claim 1 to said fuel oil.
 15. The additive of claim 1, wherein at least one of R⁶, R⁷ and R⁸ is selected from the group consisting of C₁₂-C₂₄-alkyl, C₁₂-C₂₄-alkenyl, cyclohexyl, and mixtures thereof.
 16. The fuel oil of claim 11, wherein at least one of R⁶, R⁷ and R⁸ is selected from the group consisting of C₁₂-C₂₄-alkyl, C₁₂-C₂₄-alkenyl, cyclohexyl, and mixtures thereof. 